Adds description list

[vwallen]

Builds on and closes #1383

Per #1383 (comment) this feature is inconsistently supported in screen readers (and potentially other assistive tech). The display: contents feature added a BCD key to track accessibility issues with that feature related to focused elements (#1966). I don't think that approach is needed here because that related how the browser exposed those elements to assistive tech, whereas in this case (if I'm reading this correctly) the issue is how screen readers interpret the description list elements.

[captainbrosset]

Bringing my comment over from #1383, for reference:

One thing to consider: accessibility doesn't seem to be the best with DL. See https://adrianroselli.com/2022/12/brief-note-on-description-list-support.html and https://developer.mozilla.org/en-US/docs/Web/HTML/Element/dl#accessibility
In particular, it looks like keyboard navigation isn't supported everywhere.
Baseline currently doesn't cover assistive tech (see https://github.com/web-platform-dx/web-features/blob/main/docs/baseline.md#non-goals) so this is probably fine as is, but it might be good to do a bit of research for a11y best practices with DL and add a short mention of this in the description.